The monthly sales for air conditioners were as follows.
|
Month
|
Sales
|
|
January
|
24
|
|
February
|
25
|
|
March
|
18
|
|
April
|
16
|
|
May
|
15
|
|
June
|
15
|
|
July
|
17
|
|
August
|
19
|
|
September
|
19
|
|
October
|
20
|
|
November
|
22
|
|
December
|
24
|
(a) Plot the monthly sales
(b) Forecast the January sales figure using each of the following:
(c) i) Naive method
ii) A 3-month moving average
iii) A 6 month weighted average using .1, .1, .1, 2.2, and.3, with the heaviest weights applied to the most recent months
iv) Exponential smoothing using an α = .3 and a September forecast of 18
(d) With the data given which method would allow you to forecast next March's sales.
(e) What three most popular methods are used to determine the accuracy of any given forecasting method? And in what circumstances would they be used.